This invention relates to portable antennas such as a vehicular antenna and, more particularly, to a unitary antenna structure having separate portions configured for reception of signals in different frequency bands.
Vehicular antenna systems, such as those mounted on automotive vehicles including cars and trucks, may be employed to provide a radio link for various electronic systems providing a number of functions, such as the keyless entry to the vehicle for remotely locking and unlocking the vehicle as well as turning lights and possibly the engine on and off. Additional functions include alarm activation and deactivation, cellular telephony, and radio including both AM and FM radio. Yet another function which may be employed is reception of signals received from a global positioning satellite (GPS) for navigating an automobile and for trip planning.
All of these functions are implemented with the aid of some type of a radio link requiring a transmitter and/or a receiver installed within the vehicle. The radio link for the various functions is accomplished by use of separate frequency bands designated for the individual functions. The frequency bands for these functions are as follows. The global positioning satellite operates in a frequency band of 1.2-1.6 GHz (gigahertz) with a nominal wavelength of 8.5 inches, the transmission of the GPS signal being in the nature of a spread spectrum modulation. The cellular telephony operates at a frequency of approximately 860 MHz (megahertz) and has a nominal wavelength of 14 inches. In the future, there may be microwave operation at L-Band and S-Band for satellite based cellular telephone. The AM radio operates in a frequency band 540-1600 KHz (kilohertz) and has a nominal wavelength of 1100 inches. The FM radio operates in a frequency band of 88-108 MHz, and has a nominal wavelength of 120 inches. The keyless vehicle entry operates at a nominal frequency of 315 MHz and has a nominal wavelength of 37.5 inches. It is anticipated that other functions facilitating the use and safety of motor vehicles will also become available, and that such functions will be allocated a specific band of the electromagnetic spectrum for communication with the vehicle. Presently, separate antennas are provided for accomplishing some of these functions. Some functions, such as the AM radio and the FM radio may be combined to operate with a single telescoping pole, or mast, operative as a monopole antenna.
A problem arises in that, heretofore, a vehicle, such as an automobile, must carry a variety of antennas to provide the benefits of the aforementioned functions. This is inconvenient from a point of view of manufacture and installation, as well as aesthetic appearance, and maintenance or repair of breakage or vandalism.